Posted
by
Soulskill
on Friday June 21, 2013 @03:51PM
from the not-quite-everything-is-bigger-in-texas dept.

An anonymous reader sends this quote from a University of Texas news release:
"Physicists at The University of Texas at Austin have built a tabletop particle accelerator that can generate energies and speeds previously reached only by major facilities that are hundreds of meters long and cost hundreds of millions of dollars to build (abstract). 'We have accelerated about half a billion electrons to 2 gigaelectronvolts over a distance of about 1 inch,' said Mike Downer, professor of physics in the College of Natural Sciences. 'Until now that degree of energy and focus has required a conventional accelerator that stretches more than the length of two football fields. It’s a downsizing of a factor of approximately 10,000.' ... Downer said that the electrons from the current 2 GeV accelerator can be converted into “hard” X-rays as bright as those from large-scale facilities. He believes that with further refinement they could even drive an X-ray free electron laser, the brightest X-ray source currently available to science. A tabletop X-ray laser would be transformative for chemists and biologists, who could use the bright X-rays to study the molecular basis of matter and life with atomic precision, and femtosecond time resolution, without traveling to a large national facility."

The petawatt laser is installed on a 10m long optics table, and is controlled by 1 19" server rack. Granted, that's a Big Freakin Laser (tm), but hardly half the physics building, and I'm not sure, but if I understand their explanations correctly making the accelerator longer needn't necessarily require higher power from the laser. Besides, this is the engineering phase, we'll see in 10 years or so if it's actually useful and interesting from a useful science perspective. As it stands, there are facilities that can produce X-rays at these power levels, this system just seems to be designed to put one in every major college campus, rather than having 2 or 3 in the nation.

I graduated from UT with a PhD in physics, and Mike Downer was a prof while I was there. He does "femtosecond physics" ie things you can do with extremely short pulses of laser light. Pretty cool stuf, actually. Anyway, a petawatt laser (10^15 W) fired in a femtosecond (10^-15 s) has a total energy of ~1 J per pulse...they're really not giant gizmos.

A tabletop X-ray laser would be transformative for chemists and biologists, who could use the bright X-rays to study the molecular basis of matter and life with atomic precision, and femtosecond time resolution, without traveling to a large national facility."

Two men were arrested in New York, on charges of attempted terrorism, for trying to get Jewish organizations to pay for an xray that would be mounted in a truck, aimed at Muslims, and used to make them sick or kill them.

The Jewish organizations turned them down, and contacted the FBI.

Unfortunately, there may be those who actually NEED to be charged with terrorism when dealing with Xrays like this.

If you Google "2 BeV accelerator," the first relevant hit is a scanned typewritten document [slashdot.org] from CERN.

Maybe because "BeV" is really antiquated and not too long after accelerators reached that energy level, GeV became standardized.

As far as use, there are some hard limits on current accelerator technology that requires them to be scaled up to make large gains in energy. The hope is that work like this will continue to go to higher energy levels and eventually allow for surpassing the highest energy accelerators without having to dig a large hole. Although that will be potentially quite difficult, as it i

We already have had fairly cheap "tabletop" (or small car-sized) accelerators for a long, long time. Accelerating electrons to 2GeV is not terribly complicated.

However, accelerating a LARGE number of electrons is complicated. Accelerating a large number of ions is even more so. That's why LHC is necessary - you can't hope get enough luminosity with small tools, even if you can reach the same energies.

As a result of unconventional thinking about intelligent design, I coupled thermionic emission with a Van de Graff generator in a vacuum tube for electron beam high voltage alternative energy sources to produce electricity that was rejected by the scientifi

That's some pretty impressive kookery, but actually a small VDG can be used to accelerate electrons (and presumably protons as well in the form of H+ ions). See the chapter in C.L. Stong's anthology of Scientific American's The Amateur Scientist columns, beginning on page 344. There are a few copies on Amazon, and there is also a.PDF floating around, along with the 'official' CD-ROM edition which is a pile of proprietary crap.

I keep meaning to try this, if I ever get the mechanical reliability of my own

The top of mine broke, but its quite fixable. The way it was made the top "brush" (twisted stranded wire) is soldered to a thicker wire in an "A" shape. It had two holes in the top end of the shaft, one of them cracked out. At this point the belt is a good 20 years old, but, last time I rigged it up to work for a few minutes it gives some sparks.

H+ ions eh? Just so happens I was looking at a water torch video recently (sadly, nearly everyone working on such things seems to be a crackpot who is trying to fit

Course when you really get down to it, if you are going to go through that much trouble to make a table top accelerator, it seems like it would be easier to skip the electrical energy to mechanical energy and mechanical energy to electrostatic potential steps. Seems like charging a capacitor and using some sort of cathode/annode setup..... and that is how the VDG ended up in the museum:)

Agreed, a Cockroft-Walton multiplier should be pretty easy to construct these days with HV components available on eBay.

http://rtftechnologies.org/physics/linac.htm is one of several examples of hobbyist-built particle accelerators. CW generators are pretty easy to build, the biggest issue tends to be corona suppression.

You are right. In addition for electron machines (like this one) the electrons need to be in a very small phase space to be useful for modern high brightness X-ray facilities.(small volume, small divergence, short pulse, low energy spread - 6 dimensional phase space, with good shot to shot stability.

Laser accelerators are a very interesting technology and have made huge advances in the last decade, but so far cannot replace the large machines. With continued research they may be able to do so in the future,

The energy limits for circular accelerators are set by the strength of the magnets and diameter of the ring. Even if you only have a small number of particles you're limited by the geometry of the machine.

The Luminosity is limited by how many particles you can keep on track. This becomes *harder* the bigger your accelerator. In other words, the LHC has a high luminosity *despite* it's large size, not because of it.

The problem is that you _need_ large size to store a large number of particles, they are not moving as a constant stream but in batches and you need a certain distance between them. I think a 1GeV electron cyclotron was about 5 meters in size - not exactly a field-size, but still big.

A cyclotron is a continuous accelerator that doesn't need storage capacity. That's also one advantage of the plasma accelerator in the article, it doesn't need a storage ring.Anyway, the point is there are no conventional "compact high-energy low-luminosity" accelerators. It's inevitably a trade-off between size and energy. Which is why this new technology is so interesting, as it can reach the energy levels with a much smaller system.

BTW, do you have a source? A 5m 1 GeV electron accelerator sounds a bit f

this technique, IIRC, only applies to acceleration of electrons. The primary use, as the article states, will be as a light source for bio/chem/materials research such as takes place in NSLS at Brookhaven. Beam time is always over subscribed so I'm sure there will be demand for something like this though it would be nice to have a better idea of the costs - I'm not sure this means every lab gets one or there might be one shared by an entire university or research center.

Well then, you lucky man, there is probably only one thing to be done then, if you have the stones (and think you can avoid any possible drawbacks).

If you can cook at all, take a weekend cooking class with her sometime. It'll be a mutual activity you can share, you'll get time to spend with her, you might pick up something you can serve her on special occasions for breakfast in bed (for which you'll have the gratitude of a pretty woman), and her cream gravy might improve without you being the one tha

If they can do this with an inch, imagine what one a mile wide could do. Sometimes I worry about how we can't find any evidence of other intelligent life in the universe but we see plenty of black holes...

To my understanding the detection of blackholes is vastly, imensely, easier than detection of intelligent life. It is like the ability to detect a nuclear explosion 50km away, vs a complicated formation of candles on a birthday cake at the same distance.

“I don’t think a major breakthrough is required to get there,” he said. “If we can just keep the funding in place for the next few years, all of this is going to happen. Companies are now selling petawatt lasers commercially, and as we get better at doing this, companies will come into being to make 10 GeV accelerator modules. Then the end users, the chemists and biologists, will come in, and that will lead to more innovations and discoveries.”

1. Start with 1GeV research laser plasma accelerator2. Demo 2GeV accelerator tied to one of the most powerful petawatt lasers in the world3. Promise 10GeV if funding continues for next few years...4. ???5. Profit!

The press release makes some very grand-sounding claims about replacing synchrotrons and free-electron lasers. I'm not an expert in the accelerator field but I've used these systems, and I have some idea of what the actual output needs to be in order to be useful for biologists. Specifically, it's not just the electron energies that matter, but the photon flux per unit of area. The figures for modern synchrotrons are on the order of 10^11 - 10^13 with a spot size of 100 microns or less - the very best will focus down to just a few microns. From what I can understand of the paper, they're talking about several orders of magnitude fewer photons over much larger areas. (If someone who understands this stuff better can confirm whether or not I'm reading it correctly, I'd be grateful.) The only hard free-electron laser in the US, the LCLS at Stanford, is orders of magnitude brighter than synchrotrons, and compressed into pulses on the order of tens of femtoseconds long.

It would be great if someone could build a high-intensity hard X-ray source at every big research university. But it's not the first time such claims have been made; there is (or was) a company called Lyncean that tried to build a tabletop synchrotron in the previous decade, and made similar predictions about its utility for biology. Their technology worked perfectly well from a theoretical standpoint - but it was several orders of magnitude too weak to be competitive with existing synchrotron beamlines, and too expensive to be competitive with existing laboratory X-ray sources.

(Of course this is pretty much standard stuff from university PR departments, which would always like you to believe that they're on the brink of curing caner or revolutionizing some widely used method. The actual Nature Communications article is much more sober.)

The experiment in the paper does produce X-rays, but these come naturally from the electrons oscillating in the plasma, a "plasma wiggler". When they mention it in the news article they seem to be talking about using the electron beam in a conventional wiggler, which should produce more photons. It wasn't part of the experiment though.